Ihave 7 hundreds blocks, 5 tens blocks, and 8 ones blocks. i use my blocks to model two 3-digit numbers. what could my two numbers be?

There 7 blocks of hundreds which means each such block is equivalent to 100.
There are 5 blocks of tens, which means each such block is equivalent to 10.
There are 8 blocks of ones, which means each such block is equivalent to 1.

The total of these blocks will be = 7(100) + 5(10) + 8(10) = 758

We can make several two 3-digit numbers from these blocks. An example is listed below:

Example:
Using 3 hundred block, 2 tens blocks and 4 ones block to make one number and remaining blocks to make the other number. The remaining blocks will be 4 hundred blocks, 3 tens blocks and 4 ones blocks
The two numbers we will make in this case are:

1st number = 3(100) + 2(10) + 4(1) = 324
2nd number = 4(100) + 3(10) + 4(1) = 434

The sum of these two numbers is  = 324 + 434 = 758
i.e. equal to the original sum of all blocks.

This way changing the number of blocks in each place value, different 3 digit numbers can be generated.